// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// ICU integration functions.

#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "base/lazy_instance.h"
#include "base/logging.h"
#include "third_party/icu/source/common/unicode/ucnv.h"
#include "third_party/icu/source/common/unicode/ucnv_cb.h"
#include "third_party/icu/source/common/unicode/uidna.h"
#include "url/url_canon_icu.h"
#include "url/url_canon_internal.h" // for _itoa_s

namespace url {

namespace {

    // Called when converting a character that can not be represented, this will
    // append an escaped version of the numerical character reference for that code
    // point. It is of the form "&#1234;" and we will escape the non-digits to
    // "%26%231234%3B". Why? This is what Netscape did back in the olden days.
    void appendURLEscapedChar(const void* context,
        UConverterFromUnicodeArgs* from_args,
        const UChar* code_units,
        int32_t length,
        UChar32 code_point,
        UConverterCallbackReason reason,
        UErrorCode* err)
    {
        if (reason == UCNV_UNASSIGNED) {
            *err = U_ZERO_ERROR;

            const static int prefix_len = 6;
            const static char prefix[prefix_len + 1] = "%26%23"; // "&#" percent-escaped
            ucnv_cbFromUWriteBytes(from_args, prefix, prefix_len, 0, err);

            DCHECK(code_point < 0x110000);
            char number[8]; // Max Unicode code point is 7 digits.
            _itoa_s(code_point, number, 10);
            int number_len = static_cast<int>(strlen(number));
            ucnv_cbFromUWriteBytes(from_args, number, number_len, 0, err);

            const static int postfix_len = 3;
            const static char postfix[postfix_len + 1] = "%3B"; // ";" percent-escaped
            ucnv_cbFromUWriteBytes(from_args, postfix, postfix_len, 0, err);
        }
    }

    // A class for scoping the installation of the invalid character callback.
    class AppendHandlerInstaller {
    public:
        // The owner of this object must ensure that the converter is alive for the
        // duration of this object's lifetime.
        AppendHandlerInstaller(UConverter* converter)
            : converter_(converter)
        {
            UErrorCode err = U_ZERO_ERROR;
            ucnv_setFromUCallBack(converter_, appendURLEscapedChar, 0,
                &old_callback_, &old_context_, &err);
        }

        ~AppendHandlerInstaller()
        {
            UErrorCode err = U_ZERO_ERROR;
            ucnv_setFromUCallBack(converter_, old_callback_, old_context_, 0, 0, &err);
        }

    private:
        UConverter* converter_;

        UConverterFromUCallback old_callback_;
        const void* old_context_;
    };

    // A wrapper to use LazyInstance<>::Leaky with ICU's UIDNA, a C pointer to
    // a UTS46/IDNA 2008 handling object opened with uidna_openUTS46().
    //
    // We use UTS46 with BiDiCheck to migrate from IDNA 2003 (with unassigned
    // code points allowed) to IDNA 2008 with
    // the backward compatibility in mind. What it does:
    //
    // 1. Use the up-to-date Unicode data.
    // 2. Define a case folding/mapping with the up-to-date Unicode data as
    //    in IDNA 2003.
    // 3. Use transitional mechanism for 4 deviation characters (sharp-s,
    //    final sigma, ZWJ and ZWNJ) for now.
    // 4. Continue to allow symbols and punctuations.
    // 5. Apply new BiDi check rules more permissive than the IDNA 2003 BiDI rules.
    // 6. Do not apply STD3 rules
    // 7. Do not allow unassigned code points.
    //
    // It also closely matches what IE 10 does except for the BiDi check (
    // http://goo.gl/3XBhqw ).
    // See http://http://unicode.org/reports/tr46/ and references therein
    // for more details.
    struct UIDNAWrapper {
        UIDNAWrapper()
        {
            UErrorCode err = U_ZERO_ERROR;
            // TODO(jungshik): Change options as different parties (browsers,
            // registrars, search engines) converge toward a consensus.
            value = uidna_openUTS46(UIDNA_CHECK_BIDI, &err);
            if (U_FAILURE(err)) {
                CHECK(false) << "failed to open UTS46 data with error: " << err;
                value = NULL;
            }
        }

        UIDNA* value;
    };

} // namespace

ICUCharsetConverter::ICUCharsetConverter(UConverter* converter)
    : converter_(converter)
{
}

ICUCharsetConverter::~ICUCharsetConverter()
{
}

void ICUCharsetConverter::ConvertFromUTF16(const base::char16* input,
    int input_len,
    CanonOutput* output)
{
    // Install our error handler. It will be called for character that can not
    // be represented in the destination character set.
    AppendHandlerInstaller handler(converter_);

    int begin_offset = output->length();
    int dest_capacity = output->capacity() - begin_offset;
    output->set_length(output->length());

    do {
        UErrorCode err = U_ZERO_ERROR;
        char* dest = &output->data()[begin_offset];
        int required_capacity = ucnv_fromUChars(converter_, dest, dest_capacity,
            input, input_len, &err);
        if (err != U_BUFFER_OVERFLOW_ERROR) {
            output->set_length(begin_offset + required_capacity);
            return;
        }

        // Output didn't fit, expand
        dest_capacity = required_capacity;
        output->Resize(begin_offset + dest_capacity);
    } while (true);
}

static base::LazyInstance<UIDNAWrapper>::Leaky
    g_uidna
    = LAZY_INSTANCE_INITIALIZER;

// Converts the Unicode input representing a hostname to ASCII using IDN rules.
// The output must be ASCII, but is represented as wide characters.
//
// On success, the output will be filled with the ASCII host name and it will
// return true. Unlike most other canonicalization functions, this assumes that
// the output is empty. The beginning of the host will be at offset 0, and
// the length of the output will be set to the length of the new host name.
//
// On error, this will return false. The output in this case is undefined.
// TODO(jungshik): use UTF-8/ASCII version of nameToASCII.
// Change the function signature and callers accordingly to avoid unnecessary
// conversions in our code. In addition, consider using icu::IDNA's UTF-8/ASCII
// version with StringByteSink. That way, we can avoid C wrappers and additional
// string conversion.
bool IDNToASCII(const base::char16* src, int src_len, CanonOutputW* output)
{
    DCHECK(output->length() == 0); // Output buffer is assumed empty.

    UIDNA* uidna = g_uidna.Get().value;
    DCHECK(uidna != NULL);
    while (true) {
        UErrorCode err = U_ZERO_ERROR;
        UIDNAInfo info = UIDNA_INFO_INITIALIZER;
        int output_length = uidna_nameToASCII(uidna, src, src_len, output->data(),
            output->capacity(), &info, &err);
        if (U_SUCCESS(err) && info.errors == 0) {
            output->set_length(output_length);
            return true;
        }

        // TODO(jungshik): Look at info.errors to handle them case-by-case basis
        // if necessary.
        if (err != U_BUFFER_OVERFLOW_ERROR || info.errors != 0)
            return false; // Unknown error, give up.

        // Not enough room in our buffer, expand.
        output->Resize(output_length);
    }
}

} // namespace url
